This invention relates to disk storages.
More particularly, the invention relates to a method of driving disk storage.
Still more specifically, the invention relates to a method of driving disk storage in such a manner as to eliminate, or at least minimize, scratching of the disk surface by the reading and/or recording heads of the device. The invention also relates to an apparatus for carrying out the method.
In disk storage devices, information is magnetically recorded on high-speed rotating disks and is subsequently read out while the disk is rotating. Recording and read-out are effected by magnetic recording and reading heads, respectively. During the actual recording or read-out operation, i.e. when the disk rotates at high speed, these heads "float" on a thin layer of air which is entrained by and above the disk surface; due to the presence of this layer, the heads do not contact the disk surface under those conditions.
However, the development of the air layer or cushion is a function of the disk speed. Before the disk reaches a sufficient speed, or when it drops below this speed, the air layer does not exist and the reading or recording heads can contact the disk surface which they can scratch or otherwise damage and/or on which they can deposit dirt or other contaminants. This can be counteracted by reducing the number of disk revolutions at start-up (i.e. before the disk is up to speed) and at run-out (i.e. before the disk stands still) to the maximum possible extent.
The solution to this problem for the start-up phase is not particularly vexing, since appropriate motor selection assures that the disk comes up to speed very rapidly. The run-out phase, however, presents much more of a problem because both the drive and the disk support have a substantial amount of inertia, so that a relatively long time elapses before the disk comes to a full stop. During this time, of course, the head or heads ride on the disk in contact with its surface and can scratch or otherwise damage it.
The U.S. Pat. No. 4,101,945 shows a drive spindle assembly for disk file as known per se in this field.